This invention relates to compositions useful in the manufacture of polishing pads which can be used for creating smooth, ultra-flat surfaces on items such as glass, semi-conductors, dielectric/metal composites, metals, and integrated circuits. The instant invention proposes the manufacture of polishing pads from specifically advantageous photopolymer compositions.
Polishing generally consists of the controlled wear of an initially rough surface to produce a smooth (specular) surface. One method of accomplishing this is by rubbing a pad against the surface of the article to be polished (the work-piece) in a repetitive regular motion. Frequently, a slurry or suspension of fine particles is present at the interface between the polishing pad and the work-piece.
Polishing pads have historically been fabricated from felted or woven natural fibers such as wool, urethane impregnated felted polyester on various types of filled polyurethane plastic. U.S. Pat. No. 5,489,233, the teaching of which are incorporated herein by reference in their entirety, discloses some polymers useful in the manufacture of polishing pads and desired characteristics of these pads.
The polishing rate regarding a polishing pad is controlled by a variety of variables including pressure between the pad and work-piece, velocity of the pad in relation to the work-piece, size of the particles in the slurry, hardness of the particles in the slurry and of the pad material, configuration of the pad surface, texture of the pad material, and possibly chemical reactivity between the slurry or the pad and the work-piece.
Generally macrotexture and microtexture of the pad are provided for in the pad manufacturing process. U.S. Pat. Nos. 5,081,051 and 5,216,843, the teaching both of which are incorporated herein by reference in their entirety, disclose the importance of maintaining this macrotexture. Frequently polishing pads have depended upon inhomogenity in the pad material to achieve polishing. However in order to achieve acceptable polishing the inhomogenity must be constant across the surface (throughout the body) of the pad. Many of the materials used to make pads however fall short in this regard. Thus, for example, variability in density of felt for pads or variations in filler density negatively impact polishing performance.
The inventors herein propose the use of photopolymers to create polishing pads with the appropriate texture and surface features for optimum polishing characteristics. These photopolymers provide pads with the appropriate surface texture without any substantial inhomogenity in the bulk material. The pads produced have optimum polishing characteristics and are relatively economical.